"At one point they put up on the board the most runs in a series by an Australian player and he might have been sixth or seventh on the list of all time but he's batted two or three times less than some of those guys at the top.

"It's an incredible feat and those big innings he's played as well, they've all been really important.

"In Brisbane and Perth they were match-winning and in Melbourne it was match-saving. He's been the real different between the two sides."

It came after Smith claimed one of the catches of the summer in the first session to redeem himself in the field and remove Dawid Malan.

While Smith's summer has been nothing short of phenomenal - averaging more than 150 with the bat - he has put down four crucial catches, including twice giving Malan another life.

After dropping the England left-hander on day two in Adelaide, he put down a difficult chance when Malan was on 34 on the opening day at the SCG.

Smith finally got his man in the first session on Friday, taking a screamer of a diving one-hander at second slip to dismiss Malan for 62.

"From the bowlers, we're stoked he's on our team so we don't have to bowl at him. It's crazy," Cummins said.

"But he just goes out there and from ball one he looks like he's batting for three hours already. There's no obvious weakness."